I put about bed rail level load of dirt on the truck today. Never hauled this much weight and to my knowledge, it has never hauled a load at road speed. Driving 60 on the highway and start up a grade and get slight vibration that feels like its in the drive train. Otherwise smooth. 73K miles. I'm thinking TC... What say you?

 

With that much weight you're squatting the back end quite a bit, and that difference in angle would stress your u-joints differently than they normally run. It could just be you've got old u-joints and the pending failure doesn't show up yet in regular day-to-day driving.

 

There wasn't much helper spring tension left so it was squatted on down there. Maybe it is just a u joint. Thanks for the reply.

 

I would agree on the possibility of the u-joints. My rear one was completely gone at 80k miles. I looked a few times and externally I could see or feel nothing. I finally pulled the 4 bolts out of the rear flange and dropped the shaft. Rust poured out and it was way beyond shot. I just drop the shaft every couple of years and replace them both now.